This invention relates generally to a carburetor for an internal combustion engine and particularly to improvements of the carburetor having therein a main circuit and a low-speed circuit.
It is well known for carburetor to be provided with a main circuit for supplying fuel from a fuel chamber to a main discharge nozzle and a low-speed circuit or an idle system for supplying fuel from the main circuit to a fuel discharge port through which the fuel is supplied into the air-fuel mixture induction passage of the carburetor when the engine is operated at a low engine speed or is idling. With this arrangement, however, difficulties have been encountered in that air passing through the air-fuel mixture induction passage at a high velocity sucks additional air through the low-speed circuit and introduces same into the main circuit when the engine is operated at a high engine speed and load. This additional air flow occurs as a result of the pressure differential in the air-fuel mixture induction passage between the main discharge nozzle and the fuel discharge port of the low-speed circuit. This phenomenon results in shortage of fuel discharged through the main discharge nozzle and therefore lowers the output power of the engine.